Recently, a liquid crystal display device has been widely used as an image display device of an information device such as a notebook-type personal computer, a word processor and the like, or an image display device of a video device such as a fixed or portable television, a video movie, a car navigation system and the like, by taking advantage of a characteristic in which the liquid crystal display device is small, light and thin, and consumes small electricity. And, a liquid crystal display panel mounted in these liquid crystal display devices typically has a plurality of semiconductor devices in order to achieve a small liquid crystal display device and a high-definition image. A Chip On Glass process (hereinafter, referred to as a COG process) is commonly used for mounting these semiconductor devices.
The COG process is one type of process for mounting the semiconductor devices on a substrate. Specifically, in the liquid crystal display panel to which the COG process is applied, the semiconductor devices such as a source driver, a gate driver and the like are directly mounted on a non-display region of the substrate forming the liquid crystal display panel, by means of an anisotropic conductive adhesive. The liquid crystal display panel is provided with wires through which an image signal processed at the semiconductor devices is outputted to source lines (signal lines) and gate lines (scan lines) provided on the display region, and wires through which the image signal is inputted to the semiconductor devices. And, these wires are on the same flat plane of the non-display region of the substrate forming the liquid crystal display panel. In the liquid crystal display panel thus structured, the image signal externally inputted is inputted to the semiconductor devices, and the image signal processed at the semiconductor devices is outputted to the source lines and the gate lines. Consequently, an image according to the image signal is displayed on the display region of the liquid crystal display panel.
Such liquid crystal display device typically has a structure in which the liquid crystal display panel is illuminated from behind by a built-in lighting unit for obtaining a bright display screen. And, an edge light type in which a light guiding plate is disposed on a rear surface of the liquid crystal display panel, and a linear light source such as a fluorescent discharge tube is disposed on an end face of the light guiding plate is suitably employed as the lighting unit. This is because, the edge light type advantageously achieves a thin liquid crystal display device and a light emitting surface with a highly uniform luminance, and therefore is optimal as a back light of the liquid crystal display device used in the notebook-type personal computer or the like. And, in the liquid crystal display device used in the portable television, the car navigation system and the like, the edge light type using two or more fluorescent discharge tubes, or the edge light type using an L-shaped or U-shaped fluorescent discharge tube or the like, is commonly adopted considering a portability, a high luminance thereof, and the like.
FIG. 4 is a plan view showing a structure of a conventional liquid crystal display device having the liquid crystal display panel to which the COG process is applied. And, FIG. 5 is a cross-sectional view taken along line IV-IV in FIG. 4. Herein, FIG. 4 shows a condition in which a front cover is eliminated. In FIG. 4, X-axis, Y-axis, and Z-axis directions are defined as shown in the drawing. And, in FIG. 5, as a matter of convenience, a direction of the liquid crystal display device is shown as in the drawing.
A conventional liquid crystal display device L illustrated in FIG. 4 comprises a rectangular liquid crystal display panel 1 configured to display an image according to an applied image signal, a housing 4 configured to support the liquid crystal display panel 1 in X-axis, Y-axis, and Z-axis directions, and a flexible printed circuit board 3 configured to transmit the image signal to the liquid crystal display panel 1.
As shown in FIG. 4, the liquid crystal display panel 1 is provided with a display region 1a for displaying an image, and a non-display region 1b located outside of the display region 1a. And, source drivers IC1 to IC3 and a gate driver IC4, each of which is a driving semiconductor device configured to drive the liquid crystal display panel 1, are mounted on predetermined positions of the non-display region 1b. These semiconductor devices are mounted to electrode terminals (not shown) formed to predetermined positions of the non-display region 1b by the COG process. And, a plurality of wires (not shown) extend from the electrode terminals to which the source drivers IC1 to IC3 and the gate driver IC4 are mounted, and are electrically connected to the source lines and the gate lines (not shown) provided on the display region 1a of the liquid crystal display panel 1. And, wires 2a to 2i extend in predetermined shapes from the electrode terminals to which the source drivers IC1 to IC3 and the gate driver IC4 are mounted, and are electrically connected to flexible printed circuit board connecting electrode terminals (not shown) formed on predetermined positions of the non-display region 1b. Meanwhile, wires 2a′ to 2i′ capable of being electrically connected to the wires 2a to 2i formed on the non-display region 1b of the liquid crystal display panel 1 are formed on the flexible printed circuit board 3, and electrode terminals (not shown) are formed on end portions of the wires 2a′ to 2i′ on a liquid crystal display panel 1 side. And, the liquid crystal display panel 1 and the flexible printed circuit board 3 are integral with each other such that the corresponding electrode terminals are electrically connected by means of the anisotropic conductive adhesive.
And, as shown in FIG. 4, supporting portions 4a to 4h are formed on predetermined positions of the housing 4. Each of the supporting portions 4a to 4h is formed to have a rectangular cross-section, and to protrude from predetermined positions of the housing 4 in parallel with the Z-axis and with the same height. The liquid crystal display panel 1 is disposed on the predetermined position of the housing 4 in such a manner that end faces a to d of a substrate 1B of the liquid crystal display panel 1 and adjacent end faces e and f of an opposed substrate 1A of the liquid crystal display panel 1, contact side wall surfaces of the supporting portions 4a to 4h formed on the housing 4. In other words, the liquid crystal display panel 1 is fixed on the housing 4 in X-axis and Y-axis directions by means of the supporting portions 4a to 4h. 
As shown in FIG. 5, the conventional liquid crystal display device L has a rectangular flat-plate-shaped transparent light guiding plate 5 configured to transmit light in a direction parallel to a principal surface thereof. And, a light source 6 is provided along one end face 5a of the light guiding plate 5 by a fixing means not shown. Furthermore, a reflecting sheet 7 is provided so as to enclose the light source 6 and to contact a lower surface and an opposing end face 5b of the light guiding plate 5. The reflecting sheet 7 encloses the light source 6 so as to be substantially in U-shape in cross-section. The reflecting sheet 7 is fixed to the light guiding plate 5 in such a manner that an adhesion surface 8 on one end portion of the reflecting sheet 7 is bonded to the light guiding plate 5 by a double face adhesive tape (not shown). In other words, in the liquid crystal display device L, the light source 6 is disposed along the end face 5a of the light guiding plate 5, and, the light source 6, the light guiding plate 5, and the reflecting sheet 7 compose an edge light type lighting unit UT.
A rear cover 10 is provided so as to contact a lower surface of the lighting unit UT. The rear cover 10 comprises a rectangular plate-shaped body portion 10a disposed to extend in a right-left direction, and rectangular plate-shaped vertical portions 10c and 10b formed to extend upward from right and left ends of the body portion 10a so as to have the same length. In other words, the lighting unit UT is provided so as to have predetermined spacings between the same and the vertical portions 10b and 10c of the rear cover 10, and to contact an upper surface of the body portion 10a of the rear cover 10. And, right and left housings 40a and 40b, each of which forms the housing 4, are respectively provided so as to contact left wall surfaces of the vertical portions 10c and 10b of the rear cover 10. These housings 40a and 40b comprise rectangular vertical portions 401a and 401b disposed to extend upwardly, respectively, and rectangular horizontal portions 402a and 402b disposed to extend in a right-left direction, respectively. A rectangular plate-shaped light correction sheet 9a for uniformizing light is provided so as to extend from a lower surface of a tip end portion of the horizontal portion 402a to a lower surface of a tip end portion of the horizontal portion 402b. And, the liquid crystal display panel 1 is provided so as to extend from an upper surface of the horizontal portion 402a to an upper surface of the horizontal portion 402b. The liquid crystal display panel 1 is fixed to the housing 4 in such a manner that predetermined regions thereof are bonded to the upper surfaces of the horizontal portions 402a and 402b. And, the supporting portions 4a and 4f are formed to protrude upward from predetermined positions of the horizontal portions 402a and 402b so as to have the same length. And, the liquid crystal display panel 1 is disposed on a predetermined position of the housing 4 in such a manner that the end faces a and c of the substrate 1B contact side wall surfaces of the supporting portions 4a and 4f, respectively, and the end face e of the opposing substrate 1A contacts the side wall surface of the supporting portion 4a. And, front covers 11a and 11b formed in L-shape in cross-section are provided so as to cover the non-display region 1B of the liquid crystal display panel 1 and the housings 40a and 40b. The front cover 11a is provided on an upper surface of the supporting portion 4f so as to have a minute spacing between the same and the upper surface of the liquid crystal display panel 1 and to have a minute spacing between the same and the left side wall surface of the vertical portion 401b of the housing 40b. The front cover 11b is provided on a right end face of the horizontal portion 402a of the housing 40a and on the right wall surface of the vertical portion 10c of the rear cover 10 so as to have a minute spacing between the same and the upper surface of the liquid crystal display panel 1.
The light guiding plate 5 is made of a material such as acrylic resin. And the reflecting sheet 7 is formed by a white resinous film having a light reflectivity, for example. Furthermore, the housing 4 is made of resin, such as polycarbonate, for example.
In the liquid crystal display device L thus structured, the lighting unit UT is supported by the rear cover 10, and the rear cover 10 and the light correction sheet 9a are supported by the housings 4. And, the liquid crystal display panel 1 is suitably supported by the housings 4.
And, the light emitted from the light source 6 enters the end face 5a of the light guiding plate 5. The light propagates within the light guiding plate 5 and emanates from the upper surface thereof. The light leaking out of the lower surface and the end face 5b of the light guiding plate 5 is returned into the light guiding plate 5 by means of the reflecting sheet 7. The light emanating from the upper surface of the light guiding plate 5 passes through the light correction sheet 9a, thereby achieving uniform intensity distribution. And, when the light which has passed the light correction sheet 9a is passing through the liquid crystal display panel 1, transmissivity of the light in the liquid crystal display panel 1 is controlled according to the image signal applied to the liquid crystal display panel 1, and thereby an image is displayed on the display region 1a of the liquid crystal display panel 1.
However, in the conventional liquid crystal display device thus structured, since the housing 4 is made of resin, the housing 4 is required to be formed with a certain thickness in order to satisfy mechanical strength thereof. This has impeded achievement of smallness and thinness which the liquid crystal display device L is required to provide. Recently, in order to solve the problem, an attempt has been made to form the housing 4 by a thin metal plate. However, if the housing 4 is formed by the thin metal plate, the liquid crystal display panel 1 is directly supported by metal. And, if an excessive impact stress or the like is applied to portions of the liquid crystal display panel 1 which contact the supporting portions 4a to 4h due to fall or the like after the liquid crystal display device L is finished, and in a manufacturing process of mounting the liquid crystal display panel 1, the portions of the liquid crystal display panel might break. And, when the end face of the liquid crystal display panel 1 is broken, and even one of the wires 2a to 2i provided on the non-display region 1b is damaged, the image signal is not properly transmitted, thereby causing a new problem that a normal image is not displayed on the liquid crystal display panel 1.